Musnad Ahmad 1013:27

Qutaybah ibn Sa'id narrated to us, Ya'qub ibn 'Abd al-Rahman narrated to us, from Abu Hazim, who said: I heard Sahl saying: I heard the Prophet, peace and blessings of Allah be upon him, saying: "I am your forerunner at the Basin (al-Hawd). Whoever comes to it will drink, and whoever drinks will never thirst after it again. There will certainly come to me people whom I recognize and who recognize me, then a barrier will be placed between me and them." Abu Hazim said: Nu'man ibn Abi 'Ayyash heard me while I was narrating this hadith to them, and he said: "Is this how you heard Sahl saying it?" I said: "Yes." He said: "And I bear witness regarding Abu Sa'id al-Khudri that I heard him add to it, saying: 'They are from me.' Then it will be said: 'You do not know what they did after you.' So I will say: 'Away, away (suhqan, suhqan) with those who changed [the religion] after me.'"